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Updated: Aug 18, 2026

Ex Vivo Assessment of Contractility, Fatigability and Alternans in Isolated Skeletal Muscles
Published on: November 1, 2012
Effects of fatigue on depolarization- and caffeine-induced contractures of skinned fibres
1Muscular Function Laboratory, Department of Human Nutrition, Foods and Exercise, Virginia Polytechnic Institute and State University, Blacksburg, VA, USA.
Aims:
Fatigue has been shown to cause intrinsic alterations in sarcoplasmic reticulum (SR) Ca2+ release.
Methods:
In this investigation, frog semitendinosus muscles were stimulated to fatigue, in vitro (80 Hz, 100 ms, 1 train s-1, 5 min). Immediately after stimulation, single fibres were removed and skinned using either chemically or mechanically skinning. Contralateral muscle were treated similarly but were not stimulated.
Results:
In fatigued, saponin skinned fibres, contracture responses to low [caffeine] (4-8 mm) were depressed compared with control. However, responses to high concentrations (10-15 mm) were not different between conditions. In the fatigued, mechanically skinned fibres, responses to chloride depolarization were depressed at all [chloride] (20-100 mm) compared with control.
Conclusions:
These results suggest that fatigue causes intrinsic alterations in both the SR Ca2+ release channel as well as communication between the transverse-tubule and the SR.
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